High-frequency electron discharge apparatus frequency control



Sept' 12, 1950 L. R. HILDEBRAND 2,521,719

HIGH-FREQUENCY ELECTRON DISCHARGE APPARATUS FREQUENCY CONTROL FiledMarch 14, 1944 2 Sheets-Sheet 2 gli i 36 24 l s L INVENTOR LYNN R.HILDEBRAND yTTORNEY Patented Sept. 12, 1950 HIGH-FREQUENCY ELECTRONDISCHARGE APPARATUS FREQUENCY CONTR/OL Lynn R. Hildebrand, Hempstead, N.Y., assigner to The Sperry Corporation, a corporation of DelawareApplication March 14, 1944, Serial No. 526,455

18 Claims.

This invention relates to electron discharge hollow resonator apparatusand more particularly to thermally responsive frequency controlarrangements for such apparatus.

According to the invention, exceptionally speedy frequency control of ahollow resonator device is accomplished by providing within an evacuatedenvelope containing the resonator a plurality of thermally sensitive4and electrically controlled members which act independently to vary theresonator frequency in opposite directions. Also a special resonatorfrequency adjustment operated by a manual control externally of theenvelope is provided for obtaining frequency regulation independently ofenergization of the thermally responsive members.

It is therefore a major object of the invention to provide a hollowresonator electron discharge device having novel thermally sensitivefrequency control arrangements.

Another object of the invention is to provide a cavity resonatorelectron discharge device having novel electrical frequency controlarrangements.

A further object of the invention is to provide a novel compact andefficient association of hollow resonator and associated frequencycontrol elements within an evacuated envelope.

It is a further object of the invention to provide a novel electrondischarge hollow resonator device having special electrically controlledthermally sensitive means Within van evacuated envelope containing theresonator for independently varying the resonator frequency in oppositedirections, and associated externally accessible manual frequencycontrol means for preselecting a reference frequency conditionindependently of energization of said thermally responsive means.

A further object, of the invention is to provide -a novel manuallyoperable external frequency control for varying the frequency of ahollow resonator mounted within an evacuated envelope.

It is a further object of the invention to provide novel cavityresonator electron discharge tube structure.

Further objects of the invention will presently appear as thedescription proceeds in connection with the appended claims and theannexed drawings wherein:

Fig. 1 is an elevation partly in section illustrating frequency controlmechanism of a hollow resonator device according to a preferredembodiment of the invention viewed along line l-l of Fia B;

Fig. 2 is an elevation partly in section of a portion of the frequencycontrol mechanism of Fig. l as viewed at about right angles to theshowing in Fig. l and along line 2-2 of Fig. 3;

Fig. 3 is -a section in plan along line 3--3 of Fig. 1;

Fig. 4 is a fragmentary elevation partly in section illustrating afurther embodiment of thermally responsive frequency control structurewhich may be employed in lieu of that of Figs. l and 2, viewed alongline ll-ll of Fig. 5;

Fig. 5 is a section in plan taken along line 5-5 of Fig. 4;

Fig. 64 is a fragmentary elevation partly in section illustrating thefrequency control mechanism of Fig. 4 as viewed at about right angles tothe showing in, Fig. 4, along line 6-6 of Fig. 5.

Referring now to Figs. 1 to 3, a cylindrical envelope ll, which may beof metal, is secured aS by a vacuum tight jointindicated at I2 to apronged base i3 of the usual vacuum tube type. A base structure lll isrigidly fixed to envelope Il and base i3. Passing through base structurel are the lead-in connections, one of which is shown at 5. Connection 5is sealed into base structure l0 by a suitable insulating seal 6. Toprevent strains from being transmitted to seal 6, connection 5 is formedwith recesses l at either side of seal 6, providing reduced diameterbending sections. This permits ready slight bending of connection 6,should that be necessary, as for connecting to prong 8, and alsoprevents strain by expansion of rigid connections such as 9.

A plurality of spaced posts lli and I5 upstanding from the basestructure lil within envelope l I rigidly carry an insulating supportmember I6 on which is mounted a suitable cathode or electron gun orelectron emitter assembly Il for projecting a stream of electronscoaxial with envelope Il.

A further plurality of spaced posts, two of which are illustrated at ISin Figure 2, also upstand rigidly from the base structure Il).Preferably three equally circumferentially spaced posts i8 are provided,and the upper end of each such post is reduced at i9 to extend through asuitable aperture in an annular resonator support 2 l. Beyond support orring 2 l, each reduced post end i9 is threaded as at I9 to t into atapped axial bore at the lower end of a short post 22 so that support 2lis rigidly clamped between posts I8 and 22. The upper end 23 of eachpost` 22 is reduced at 23 to extend through a suitable aperture in asecond annular support member 2t, and threaded for receiving a nut 25whereby 3 support member or ring 24 is fixed to the top ends of post 22.

Posts I8 and 22 and support members 2l and 24 thus provide a sturdynon-microphonic frame upstanding from the base, and substantially allthe parts within envelope l, except the reilector to be described, aremounted on this frame. Annular members 2| and 24 are parallel to eachother, and preferably coaxial with the electron stream from cathode Il.

A flat shallow cylindrical hollow or cavity resonator member 25 is xedto support ring 2|, as by soldering its peripheral side wall 2l directlyto the annular internal surface of support ring 2|. Resonator 26 isthereby mounted on ring 2| with its axis coincident with that of theelectron stream.

Opposite resonator end walls 2S and 29 are flexible, preferablycomprising generally parallel, annularly crimped, integral radiallyinward extensions of side wall 2. Walls 28 and 29 are of resilienthighly conductive material, such as beryllium copper, phosphor bronze,other copperplated metals or even copper itself, so as to be suicientlyresilient to tend to retain its illustrat'ed preformed shape againstsmall displacements, a useful property in the invention, as will appear.

Walls 28 and 29 are centrally apertured in alignment, and the aperturein lower wall 28 has secured thereto a small collar insert 3| on whichis mounted a wire mesh or other form of grid 32. Similarly a collar 33secured Within the aperture in upper wall 29 has secured thereto asecond similar grid 35. Grids 32 and 3d are portions of two similartranslated spheres and coaxial with the electron stream, and are thusprebowed so as tov prevent undesired distortion by buckling when heatedby electron impact.

A centrally apertured radially extending plate 35 has its innerperiphery suitably clamped by collar 33 to the central region of upperresonator wall 29. An inverted U-shaped bracket Sil has the ends of itsdepending legs fixed as by welding to plate 35. Bracket 38 isresiliently connected to support ring 24;. as by a pliuality of radiallyextending spring levers 3l having their outer. ends staked c-r similarlyfixed to ring 24 (Fig. 3) and their inner ends slidably projectingthrough suitable parallel longitudinal slots 38 formed in a smalltubular collar 39 rigid with the bridge of bracket 35. Each spring lever31 is preferably formed with an intermediate coil fil so as to increaseits effective lengthand strength.

Spring levers 3'! combine to urge bracket 36 downwardly, thereby tendingto urge grid 3i! toward grid 32. This downward displacement of grid 34is resisted by the resiliency of wall 29 and also by a pair ofthermally-extensible flexible wires or strips 4-2 which have their lowerends anchored to plate 35 as at 43 (Fig. 2) and their upper ends weldedor similarly xed to opposite ends of a short conductor bar 44 centrallyimbedded in an insulating body 45 of glass or the like.

A tension spring 46 is connected at its lower end to an eye member 4lrigid with glass body 45 and at its upper end to a suitable pin 48 rigidwith the bridge of an elongated bifurcated support 49 which has thelower ends of its arms secured to ring 2.6i as by nut 2E and machinescrew l.

A second conductor bar 52 centrally imbedded in glass body 65 has itsopposite ends welded to 4 the upper ends of a second pair of thermallyresponsive flexible wires or strips 53 which have their lower endsanchored to ring 2|, as by suitable terminals clamped at 5!! betweenpost 22 and ring .l and at 55 by machine screw 5S (Fig. 2).

Referring again to Fig. l, a centrally apertured plate 5'! has its innerperiphery clamped by collar 3| to the central region ol lower resonatorwall 28. At diam'etrically opposite regions, plate 5l has rivetedthereto the lower ends of upstanding push rods 5B and 59 which extendfreely through suitable apertures in rings 2l and 2f; and have theirupper ends similarly riveted to the lower terminals of the divergingarms of a second bifurcated support 6| disposed in a plane perpendicularto that of support 49. Supports 49 and 6| are arranged in substantiallynested relation for economy in space and material.

A compression spring 52 is interposed between the adjacent bridgeportions of supports 49 and 5|, and' reacts against support lltv to urgesupport 6| upwardly. Thus spring 52 tends to urge grid 32 toward grid34.

Upward displacement of support 6| is opposed and controlled byexternally accessible manually adjustable arrangements. The upper end ofenvelope is sealed vacuum tight by a flexible diaphragm 63 which may bean annularly crimped disc (preferably steel for greater ilexibility andlonger life before mechanical rupture) similar to walls 28 and 29.Diaphragm 93 carries a central button GG having a recessed lower face 64within envelope adapted to t with an upstanding conical seat 65 on thebridge of support (il.

Externally of envelope Il, button E4 carries a rigid upstanding threadedpost 6G which may be integral with button till if desired. A rigid endclosure member 61 protectively encloses the end of envelope ll beyonddiaphragm G3, and the shank S8 of an external manual control knob 59 isrotatably mounted on closure member 6l. Shank 58 has an internalthreaded bore fitting with post 6E and is held against axialdisplacement when rotated. Hence, when knob 69 is rotated, button 64 ispositively axially displaced relative to envelope and this motion ispositively transmitted within envelope I by support di', push rods 58,59, and plate 5l to displace grid 32 toward or away from grid 34'.Closure 6l is formed with an air escape aperture 7| to permit thisadjustment.

The above manual adjustment is made independently of any other frequencycontrol provision. A differential screw arrangement may be used here togain ner control.

A suitable arcuate metal reflector electrode l2 is rigidly mountedwithin envelope in axial alignment with the electron stream emergingthrough grid 3d. Reflector I2 is xed to an insulation disc 73 secured asby a sheetI metal rim 'M upon a support plate 'l5 which extends throughthe space within bracket t6 and is secured as by fastening elements 'I8upon the upper ends of a pair of posts '11 upstanding from the basestructure Ill. A suitable potential is applied to reflector l2, as bylead 78.

The various elements adapted for electrical energization within envelopeare suitably connected to base prongs, and these connections are notshown since their details do not comprise part of the present invention.A suitable coaxial line 'E9 coupled to the resonator field by a loop 8|extends through the base in vacuum tight relation and enables extractionof high frequency energy from resonator 26.

In operation, with wires 42 and 53 de-energized, the gap between grids32 and 34 may be varied micrometrically by manipulation of knob 69 topreset the natural frequency of the resonator at an operating point fromwhich the thermally sensitive wires 42 and 53 may be selectivelyeffective to change the resonator frequency in opposite directions, aswill appear. Compression spring 62 insures that this adjustment has nomechanical play or lost motion.

Assume that wires 42, which are electrically and mechanically inparallel for uniformly distributing the frequency control forces, areheated by passage of current therethrough while wires 53 remainunenergized. Wires 42 elongate, thereby permitting radial springs 37 todisplace grid 34 against the resistance of flexible wall 29 to decreasethe gap between grids 32 and 34 and thus decrease the resonant frequencyof resonator 26, with a corresponding change in output frequency of thedevice. During this action glass body 45 is held against displacementdue to wires 53 which oppose the pull of spring 46, so that the upperends of wires 42 are effectively stationary.

A decrease in energization of wires 42 will permit them to contract andthus will cause grid 34 to move away from grid 32, thereby increasingthe resonant frequency of the resonator 26. This type of action is usedin prior devices, but has several disadvantages. Firstly, it isnecessary to maintain the thermal wires at half energization, when atnormal or mid-frequency, in order to be able to tune in both directionsby increase or decrease of their excitation. This causes an undesirablecontinuous power drain, and also renders the device sensitive to changesin ambient temperature, since the length of the thermal Wires depends ontheir temperature, which in turn depends on their power dissipation andthus on the ambient temperature.

A further and more serious disadvantage resides in the fact that unequalrates of tuning are obtained in the two directions. Tuning .byincreasing excitation is quite fast, as is desirable in such uses asautomatic frequency control Where it provides a sensitive and accuratefrequency adjustment without substantial overshooting of the finaldesired frequency. However, tuning by decreasing excitation isrelatively slow with corresponding disadvantages.

These disadvantages of the prior devices are substantially overcome bythe present invention, in which, as will be seen, tuning in bothdirections is effected by increase in thermal wire excitation. Thus,assume that wires 53, which are also electrically and mechanically inparallel, are heated by passage of electric current therethrough whilewires 42 remain iixedly energized. Wires 53 elongate, thereby permittingtension spring 46 to displace glass body 45 upwardly. This motion istransmitted through wires 42 and plate 35 to increase the gap betweengrids 32 and 34 and thus increase the frequency of resonator 26.

Any suitable electrical circuit connected to the socket into which thebase prongs are inserted can be employed to selectively pass currentthrough either of the conductor pairs 42 or 53, or to energize one morethan the other as desired. No illustration of such circuits is herenecessary to understand the present invention which concerns improvedfrequency control and other 'structural features of the hollow resonatordevice.

Thus, after the operating frequency point of the resonator has beenmechanically preset, manual or automatic selective energization of thethermally sensitive wire pairs 42 or 53 may be utilized for quicklyvarying the resonator frequency within an appreciable range. The use ofpairs of symmetrically disposed wires 42 and 53 insures that relativedisplacement of grids 32 and 34 is substantially parallel which ishelpful to reliable frequency control.

The invention enables a saving in power over prior thermal tuningemploying single directional tuning with one or more wires or strutswhich must be kept energized to substantially half normal fullelongation in order to maintain the desired operating point, since inthe present invention both wires are normally unenergized, and thenormal frequency is set manually.

Also, better temperatinre stability is mentioned, since any change innormal temperature of wires cl2 is accomplished by a correspondingchange for wires 53. Thus wires 42 and 53 extend substantially equally,resulting in no frequency change.

It will be noted that in the embodiment discussed above with respect toFigs. 1-3, the thermal tuning wires 42 and 53 act to change the tuningin respective dierent directions while actuating the same grid 34 ofresonator 26, and the mechanical tuning by control 65 operates only onthe other grid 32 of resonator 26. The modification illustrated in Figs.4-6, on the other hand, utilizes respective different grids forthermally tuning in respective directions and has the mechanical ormanual tuning control operative together with one of the thermalcontrols upon one grid, but independently thereof.

Thus, referring to Figs. 4 6, elements corresponding to those of theprior figures are given the same reference character. In Figs. 4 6, thetuning wires 53 have been replaced by corresponding tuning wires 53',and a single tuning Wire 42', which may be also a rigid thermally fexpansible strut where desired, replaces wires 42.

The support 43 of Figs. 1-3 has been replaced by a ring having a largeinternal opening :which is supported upon the rods 85, fixed to support24. Ring 85 is thereby rigidly supported from the base. Ring 85 ispreferably of insulating material and rigidly supports one end of eachof the wires 53. These wires 53 extend freely through openings 9| and 92in supports 24 and 2|, respectively, and are fixed at their ends renmote from ring 85 to the conducting plate 57 which, in turn, is xed tothe grid 32. In the present embodiment, plate 5'! is urged toward thelower support i6 by means of tension springs such as 93. Wires 53 havetheir upper ends suitably connected to an energization conductor 6Ipassing through one of the base prongs 6, as in the prior modifications.The lower ends of wires 53 are then grounded by connection to the plate51 which supplies a ground return for the energizing current, so thatwires 53' are electrically in parallel. It will be seen that bysupplying suitable excitation to the wires 53', they will be caused toincrease in length, permitting springs 93 to draw plate 5l and grid 32downward and away from grid 34, whereby the resonant frequency ofresonator 26 and consequently the out-y put frequency from the device isincreased.

The thermal frequency control of the resonator in the opposite sense isentirely independent from that just described. Thus, the insulatingbloc-k 45', corresponding to block 45 of preceding figures, is hungdirectly from the button 64 in diaphragm 63, as by means of the loopfl'l fixed to the block 45 and a loop S4 fixed to button 64, replacingthe conical seat 54 of prior gures.

Thermal wire 42' is then rigidly fastened at one end to the insulatingblock 45. The other end of wire 42' is centrally xed to the bridge 3Gwhich is rigidly connected vto the grid 34 through the plate 35 as inthe prior figures. It will be seen that effectively the presentmodification merely has replaced the wires 42 of the prior gures whichwere connected to plate 35, with a single wire 42 connected to thebridge 35. The springs 3l again urge bridge 3E and grid 34 downwardlytoward grid S2. The upper end of Wire 42 is again suitably connected toan energization lead and one ci the base pins. The lower end is groundedby connection to bridge 3B. Upon energization of wire 42', it willincrease in length, permitting spring 31 to urge grid 34 toward grid 32thereby decreasing the output frequency from the device. This is seen tobe independent from the control of grid 32.

For manual control of the output frequency, it is merely necessary toactuate knob 69, which causes displacement of button til as discussedwith respect to the prior figures. Wire 42 is now of xed length, so thatany displacement of button 64 permits springs 31 to produce a, corro--sponding displacement of bridge 35 and grid 3i. Springs 3l assurepositive motion of grid 3Q in both directions without backlash. Theremaining portions of the device of Figs. 3-6 are similar to those ofthe prior figures and need not be repeated in detail.

If desired, of course, wire 42 could be replaced by a rigid strut 4whichis also thermally extensible in the same manner. When such a strut isused, its upper end may be connected to button 64 and then the springsE? may be eliminated, since positive action is obtained in bothdirections of motion. However, it is still preferable to utilize thespring 37 in this case, in order to overcome any slack in the threads ofscrew 6G and to help centralize the bridge 33 and grid 34.

Also, if desired, the upper end of wire 42 could be maintained fixed asby connection t0 a member rigid with supports Zfl and 2i. In such case,ring 85 would no longer be rigidly supported from 24, but would besupported from button G4. in this way, the manual control 59 wouldactuate grid 32 instead of grid 34 as illustrated in the drawings.

In referring to the change of the resonant frequency of resonator Z inone sense, it will be understood that such a change in frequency mayinvolve either an increase or decrease of the resonant frequency oiresonator 2li. However, a change in the resonant frequency in anopposite sense implies that the frequency is changed in a directionopposite to that specified in connection with the frequency change inone sense. For instance, if the change of frequency in one sense isconsidered to be an increase of frequency, then a change of frequency inan opposite sense indi- Cates a decrease or" frequency.

Since many changes could be made in the above construction and manyapparently widely dierent embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above descriy 'ion or sla in the accompanying draningsshall be inte ated as illustrative and nit in a limiting sense.

lill

What is claimed is:

1. High frequency apparatus comprising a hollow resonator mounted on asupport and having two spaced wall portions each movable relative tosaid support, a manual control member, motion-transmitting meansconnecting said member with one of said wall portions, saidmotiontransmitting means comprising thermally extensible means toelongate upon electrical energizetion thereof to move one of said wallportions in a given direction, and further similar thermally extensiblemeans operably connected to the other of said wall portions forselectively moving said other wall portion independently and in anopposite direction from the movement of said one wall portion producedby said first thermally extensible means upon the electricalenergization of said further extensible means, whereby the frequency ofsaid resonator may be independently varied in opposite directions bysaid two thermally extensible means and may be further adjusted by saidmanual member.

2. High frequency apparatus comprising a hollow resonator mounted on asupport and having two spaced wall portions each movable relative tosaid support, a manual control member, motion-transmitting meansconnecting said member with one of said wall portions, saidmotion-transmitting means comprising thermally extensible means adaptedto vary in length in response to varying electrical excitation thereof,and further similar thermally extensible means operably connected to theother of said Wall portions for selectively moving said other Wallportion independently and in an opposite direction from the movement ofsaid one wall portion produced by said first thermally extensible meansupon the electrical energization of said further extensible means,whereby the frequency of said resonator may be independently varied inopposite directions by said two thermally extensible means and may befurther adjusted by said manual member, said last-named means includinga manually actuatable control member external of said envelope, andmotiontransmitting means connecting said member to one of Said walls,said motion-transmitting means including said thermally extensiblemeans, whereby said one wall may be actuated selectively by said manualmember or by energizing said thermally extensible means.

3. High frequency apparatus comprising a support, a hollow resonatormounted on said support having a first Wall portion movable for varyingthe oscillation frequency of said resonator, a mounting member disposedadjacent said support, first means including a rst flexible thermallysensitive expansible and contractibie member for increasing thefrequency of said resonator upon energization of said iirst member,second means including a second flexible thermally sensitive expansibleand contractible member for decreasing the frequency of said resonatorupon energization of said second member, each of said members having oneend anchored to said mounting member in electrically insulated relation,means connecting the other ends of said flexible members to said supportand said first movable resonator wall portion respectively, meansresiliently connecting said mounting means to said support formaintaining said flexible members taut; and manually operable means oporily connected to very thc oscillation frequency ol said resonatorindependently of actuation ol' said thermally sensitive 9 means, saidlast-named means comprising a second movable wall portion on saidresonator and a manually manipulatable device operably connected to saidsecond wall portion; said second wall portion being spaced from saidfirst wall portion.

4. High frequency apparatus comprising a support, a hollow resonatormounted on said support having rst and second spaced wall portionsseparately movable for independently varying the oscillation frequencyof said resonator, a mounting member disposed adjacent said support, apair of flexible thermally sensitive expansible and contractible memberseach having one end anchored to said mounting member in electricallyinsulated relation, means connecting the other ends of said flexiblemembers to said support and said rst movable resonator wall portionrespectively, means resiliently connecting said mounting means to saidsupport for maintaining said flexible members taut, said members varyingupon energization the fre quency of said resonator in opposite senses,manually operable means operably connected to said second wall portionto vary the oscillation frequency of said resonator independently ofactuation of said thermally sensitive means, and a second pair offlexible thermally sensitive members each being electrically andmechanically in parallel with one of said rst pair.

5. High frequency apparatus Comprising a support, a hollow resonator`mounted on said support and having two spaced wall portions movablerelative to said support, a body of in sulating material resilientlyconnected to said support, two thermally sensitive expansible andcontractible flexible frequency control members having correspondingspaced ends secured to said insulating body, means securing the otherends of said flexible members to said support and one of said movableresonator wall portions respectively, one of said members varying uponenergization the frequency of said resonator in a first direction, theother of said members varying upon energization the frequency of saidresonator in a second direction, said second direction being opposite tothat of said first direction, and means for independently moving theother of said resonator wall portions for effecting further frequencycontrol of said resonator.

6. High frequency apparatus comprising an evacuated envelope, a support,a hollow resonator mounted on said support within said envelope andhaving two spaced wall portions each movable relative to said support,thermally sensitive means within said envelope operably connected to oneof said wall portions for selectively oppositely moving uponenergization said one wall portion for independently varying theresonator frequency in opposite directions, and externally accessiblemanually operable means on said envelope connected through said envelopeto the other of said movable wall portions for further independentlyvarying the resonator frequency.

'7. The apparatus defined in claim 6, wherein said thermally sensitivemeans comprises two independently energizable sets of expansible andcontractible flexible conductors operably connected to said support andsaid one wall portion respectively at corresponding ends and havingtheir other ends resiliently connected to said support.

8. High frequency electron discharge apparatus comprising an evacuatedenvelope, a conductive hollow resonator body within. said envelope andhaving independently movable, generally parallel end walls formed withaligned electron-permeable regions, means in said envelope forprojecting an electron stream through said regions, and means includinga pair of separately acting thermally actuatable longitudinallyextensible members and motion transmitting means Within said envelopefor independently displacing each of said regions with respect to saidbody, whereby the width 'of the gap between said regions may be variedto selectively vary the resonator frequency. v

9. Apparatus as in claim 8, wherein a manually actuatable means externalof said envelope is provided for cooperating with said motiontransmitting means for displacing one of said walls, and said extensiblemembers are adapted to independently displace the'other of said walls.

10. High frequency apparatus comprising a support, a hollow resonatormounted on said support and having two spaced wall portions each movablerelative to said support, and a pair of thermally sensitiveindependently actuatable means for selectively independently movingsaidI two wall portions for independently varying the" resonatorfrequency in opposite directionsjthe ends of each independentlyactuatable means being connected to said wall portions respectively.

11. High frequency apparatus comprisinga conductive hollow resonatorbody having exible generally parallel end walls formed with alignedelectron-permeable regions, and means coupled to said walls forindependently displacing each of said regions with respect to said body,yfor varying the width of the gap between said regions to selectivelyvary the resonator frequency.

12. Apparatus as in claim l1, wherein vsaid displacing means includestwo thermally actuat" able longitudinally extensible means, one ofsaid"V means for displacing one of said walls and the" other forindependently displacing the other of said walls.

13. Apparatus as in claim 11, wherein said motion transmitting meansincludes manually actuatable means for displacing one of said walls andmeans for energizing one of said longitudinally extensible means forindependently displacing the other of said Walls.

14. High frequency apparatus comprising a cavity resonator having a pairof flexible wall portions separately movable for independently varyingthe resonant frequency of said resonator, means including a thermallyextensible member coupled to one of said flexible wall portions forflexing said wall portion upon electrical energi- Zation of said memberto produce tuning of said resonator, manually adjustable means coupledto said one wall portion through said extensible member for manuallyadjusting said one wall portion and thereby. independently tuning saidresonator, and a further thermally extensible member coupled to saidresonator for exing the other of said flexible wall portions uponelectrical energization of said further member, whereby further tuningof said resonator is effected.

15. High frequency apparatus comprising a cavity resonator having a pairof independently movable flexible wall portions each adapted to vary theresonant frequency of said resonator upon exing thereof. manuallyadjustable tuning control means coupled to said resonator for flexingone of said wall portions to produce tuning of said resonator, andbi-directional electrically excited thermally actuatable tuning meansincluding a pair of electrically excited thermally extensible memberscoupled to the other of said Wall portions for producing movementthereof in one direction upon increase in excitation of one of saidmembers and in opposite direction upon increase in excitation of theother member.

16. High frequency resonator apparatus comprising a cavity resonatorhaving a pair of ilexible Wall portions independently movable forseparately adjusting the resonant frequency of said resonator, manuallyactuated means coupled to one of said wall portions for producingcontrollable flexing thereof for tuning said resonator, a linearlyextensible thermally actuatable electrically excitable member coupled toone of said Wall portions, means connected to said member for causingsaid member to produce move ment of said last-named one wall portion ina given direction upon increase in excitation of said member to varytuning of said resonator in. one sense, a further linearly extensiblethermally actuatable electrically excitable member coupled to one ofsaid wall portions, and means coupled 1 to said latter member forcausing said latter one wall portion to flex upon increase in excitationof said further member in a direction to produce variation in tuning ofsaid resonator in the opposite sense, said manually actuated means beingconnected to one of said Wall portions through one of said linearlyextensible thermally actuatable electrically excitable members, wherebytuning of said member may be independently effected either by said tWomembers or by said manually controllable means.

17. High frequency resonator apparatus cornprising a cavity resonatorhaving a xed body portion and a pair of independently exible wallportions, bi-directional thermally actuated tuning means having a pairof independently electrically excitable thermally extensible elementscoupled to said resonator for producing variation in resonant frequencythereof in one sense upon increase of excitation of one of said membersand for producing variation of said resonant frequency in opposite senseupon increase of excitation of the other member, and manuallycontrollable means coupled to said resonator for producing tuningthereof independently of the excitation of said members.

18. Apparatus as dened in claim 17 wherein said pair of thermallyextensible elements are connected to one of said flexible wall portionsof said resonator, said manually controllable means being connected tothe other of said Wall portions of said resonator.

LYNN R. HILDEBRAND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,658,953 Theremin Feb. 14, 19281,884,591 Davis Oct. 25, 1932 2,079,809 Kul-lle May 11, 1937 2,146,365Batchelor Feb. 7, 1939 2,183,215 Dow Dec. 12, 1939 2,251,085 Unk July29, 1941 2,259,690 Hansen et al. Oct. 21, 1941 2,380,496 Beard July 31,1945 2,408,817 Snow Oct. 8, 1946 2,414,496 Varian et al. Jan. 21, 19472,414,785 Harrison et al Jan. 21, 1947 2,434,294 Ginzton Jan. 13, 19482,468,145 Varian Apr. 26, 1949 FOREIGN PATENTS Number Country Date537,518 Great Britain June 25, 1941

